1. Field of the Invention
This application relates to a structure for providing shelter from the elements, such as an umbrella, and mechanisms for altering where such shelter is provided, particularly as conditions change.
2. Description of the Related Art
Umbrellas have been developed to provide shelter from the elements and are particularly useful in outdoor seating areas, such as on a backyard patio. Typically, an umbrella comprises a support pole and a retractable canopy positioned at the top of the pole for providing shade. Basic umbrellas have a canopy fixed in a plane perpendicular to the axis of the support pole. However, such umbrellas have limited ability to place the shade where it is desired. The position of the sun varies throughout the day and the year. In some umbrellas, an upper portion of the pole is tiltable so that the canopy can also be tilted to respond to variation in the sun's position during a day. Such umbrellas only tilt in one or two directions and in the same plane with respect to the pole. It is highly desirable to provide more flexibility in where the shade may be placed by having not only such tilting ability, but also some rotation about the vertical axis defined by the umbrella pole. A few umbrella designs enable rotation of an upper portion of an umbrella about a vertical axis to respond to variation in the sun's position.
For example, U.S. Pat. No. 6,575,183 discloses a sunshade for which an upper portion can rotate relative to the ground. The sunshade of the '183 patent comprises a post consisting of an upper supporting tube, a lower supporting tube, a canopy frame mounted to the upper supporting tube, and a device for rotating the canopy frame relative to the ground. The canopy is mounted on a rod which is pivotally mounted via a joint to the upper support pole. The rotating device has a complex structure that includes a sleeve that is movable downward to disengage a clutch mechanism to enable rotation of the sleeve. Rotation of the sleeve in turn causes rotation of four gear members mounted inside the sleeve. Rotation of the four gear members causes rotation of an elongated internal tube, which, in turn, causes rotation of the joint and thereby the canopy. Thus the elongated internal tube transmits the torque of the sleeve upward over a significant distance. The '183 patent sunshade also includes a canopy operating crank mechanism, which includes a spool, and a cable that extends upwardly to the canopy.
The foregoing construction is disadvantageous in several aspects. First, the elongated internal tube is subject to strain due to its length and the turning force it applies to the joint to turn the relatively large and heavy canopy. Also, as discussed above, the sleeve and associated force transmission member are located above the crank mechanism that operates the canopy frame. The arrangement of these components requires the cable of the crank mechanism to be threaded through various clutch and torque transmission components. This further complicates the structure by requiring passages to be formed through these components to receive the cable. Also, the rotating clutch and force transmission components are likely to rub on the non-rotating cable, potentially causing the sunshade to become jammed or the cable to wear much faster than other components.
U.S. Pat. No. 4,622,987 describes a shade umbrella that can be rotated about a vertical axis. A cam button protrudes through an opening adjacent each end of two annularly mated shaft portions supporting the umbrella. In particular, the button extends through an upwardly extending inner shaft portion and a downwardly extending outer shaft portion. The outer shaft portion abuts a flange coupled with the inner shaft portion to support the inner shaft portion. The cam button is resiliently held in the opening by a torsion spring and is manually depressed by a thumb button that extends to the outside surface of the outer shaft portion. The thumb button can be manually depressed to move the cam button inwardly to release the outer shaft portion, permitting manual rotation of the inner shaft portion and the upper portion of the shade umbrella to control the location of shade provided thereby. After the thumb button is depressed with one hand, a user must take hold of an upper portion of the umbrella with the other hand to provide such rotation.
Two-handed operation is inconvenient. Also, repositioning the umbrella is awkward from any position other than a position on the side of the sunshade where the thumb button is located. Moreover, rotation of the upper pole portion is cumbersome, because there apparently is no limit on the travel of the thumb button. If the thumb button is over-depressed, rotation of the upper pole portion will be prevented. Additionally, such thumb buttons are uncomfortable to use.